Basic Book Design/Gender

Don’t use they, them, or their to replace he, she, him, her, his or hers. "They" and "their" are considered plural (and only plural) by many people however their usage for the 3rd person singular is becoming more common. "He," "she," "him," and "her" are singular.

However, in modern times the "singular they" is becoming more accepted by casual readers and professionals alike. For example, the Washington Post Style Guide now endorses the singular they[1], and the American Dialect Society word of the year in 2015 was the singular they[2]. This is especially important because some transgender people use exclusively they/them pronouns, and it would be rather difficult to talk about them if their pronouns were deemed unacceptable.[3]

It should be noted that when referring to a person who uses singular they, "they" is still syntactically plural.[4] For example: